M.Sc. / Carbon nanotubes (CNTs) have been of utmost scientific interest since their discovery in 1991 by a Japanese physicist - Sumio Iijima. This is due to their extraordinary properties which make them one of the most promising options for the design of novel ultrahigh strength polymer nanocomposites. It is believed that the high aspect ratio, mechanical strength, and high electrical and thermal conductivity of these CNTs will enhance the performance of many polymer / CNT nanocomposites and open up new applications. However, poor dispersibility and lack of interfacial adhesion of the CNTs in the polymer matrix have remained a challenge towards fabrication of these nanocomposites. This has been due to the atomically smooth surface of the nanotubes and their intrinsic van der Waals forces which make them chemically inert. This study was aimed at exploring this concept by using novel phosphorylated multiwalled carbon nanotubes (p-MWCNTs) and polyvinyl chloride (PVC) polymer. Phosphorylation of MWCNTs has been successfully achieved in our laboratories, with the p-MWCNTs showing improvement in thermal stability. PVC on the other hand, is the world’s second largest thermoplastic material and has physical properties that are key technical advantages for its use in various and diverse fields such as building and construction, electronics, food packaging and in medical applications. A novel solvent-free method was used to synthesize p-MWCNTs / PVC nanocomposites. MWCNTs were synthesized by nebulized spray pyrolysis, a modification of catalytic vapour deposition and purified by soxhlet extraction using toluene. This method proved to be convenient and economical, producing a high yield of carbon nanotubes. The MWCNTs were phosphorylated with alkylazido phosphonate compounds through a 1,3-dipolar cycloaddition reaction between the phosphonate azides and the C=C bonds of the MWCNTs, with nitrogen loss occurring upon thermolysis. These p-MWCNTs were then melt compounded with PVC to form the p-MWCNTs / PVC nanocomposites. vii The phosphorylation of the MWCNTs and their dispersion in the PVC matrix were characterized by FTIR, SEM, TEM and Raman spectroscopy. Thermal analysis of the nanocomposites by TGA and DSC showed an enhanced thermal stability when comparing the nanocomposites with neat PVC. The modulus of the MWCNTs / PVC nanocomposites increased whilst there was a reduction in their tensile strength, indicating a decrease in polymer toughness.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uj/uj:7198 |
| Date | 13 September 2011 |
| Creators | Mkhabela, Vuyiswa J. |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
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